title: Temporary organ displacement coupled with image-guided, intensity-modulated radiotherapy for paraspinal tumors.
abstract: BACKGROUND
  To investigate the feasibility and dosimetric improvements of a novel technique to temporarily displace critical structures in the pelvis and abdomen from tumor during high-dose radiotherapy.
  
  
  METHODS
  Between 2010 and 2012, 11 patients received high-dose image-guided intensity-modulated radiotherapy with temporary organ displacement (TOD) at our institution. In all cases, imaging revealed tumor abutting critical structures. An all-purpose drainage catheter was introduced between the gross tumor volume (GTV) and critical organs at risk (OAR) and infused with normal saline (NS) containing 5-10% iohexol. Radiation planning was performed with the displaced OARs and positional reproducibility was confirmed with cone-beam CT (CBCT). Patients were treated within 36 hours of catheter placement. Radiation plans were re-optimized using pre-TOD OARs to the same prescription and dosimetrically compared with post-TOD plans. A two-tailed permutation test was performed on each dosimetric measure.
  
  
  RESULTS
  The bowel/rectum was displaced in six patients and kidney in four patients. One patient was excluded due to poor visualization of the OAR; thus 10 patients were analyzed. A mean of 229 ml (range, 80-1000) of NS 5-10% iohexol infusion resulted in OAR mean displacement of 17.5 mm (range, 7-32). The median dose prescribed was 2400 cGy in one fraction (range, 2100-3000 in 3 fractions). The mean GTV Dmin and PTV Dmin pre- and post-bowel TOD IG-IMRT dosimetry significantly increased from 1473 cGy to 2086 cGy (p=0.015) and 714 cGy to 1214 cGy (p=0.021), respectively. TOD increased mean PTV D95 by 27.14% of prescription (p=0.014) while the PTV D05 decreased by 9.2% (p=0.011). TOD of the bowel resulted in a 39% decrease in mean bowel Dmax (p=0.008) confirmed by CBCT. TOD of the kidney significantly decreased mean kidney dose and Dmax by 25% (0.022).
  
  
  CONCLUSIONS
  TOD was well tolerated, reproducible, and facilitated dose escalation to previously radioresistant tumors abutting critical structures while minimizing dose to OARs.
authors.affiliation: Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10065, USA.
authors.forename: Evangelia
authors.initials: E
authors.lastname: Katsoulakis
authors.forename: Stephen B
authors.initials: SB
authors.lastname: Solomon
authors.forename: Majid
authors.initials: M
authors.lastname: Maybody
authors.forename: Douglas
authors.initials: D
authors.lastname: Housman
authors.forename: Greg
authors.initials: G
authors.lastname: Niyazov
authors.forename: Nadeem
authors.initials: N
authors.lastname: Riaz
authors.forename: Michael
authors.initials: M
authors.lastname: Lovelock
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Spratt
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Erinjeri
authors.forename: Raymond H
authors.initials: RH
authors.lastname: Thornton
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Yamada
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D057785:Catheters; D003287:Contrast Media / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007472:Iohexol / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D009369:Neoplasms / Q000532:radiotherapy*; D058958:Organs at Risk / Q000528:radiation effects*; D064170:Paraspinal Muscles; D011832:Radiation Injuries / Q000517:prevention & control*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects / Q000379:methods*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D003287:Contrast Media; D007472:Iohexol